Main frame structure for airfoils or the like



Aug. 28, 1945. M. WATTER I 2,383,634

- MAIN FRAME STRUCTURE FQR AIRFOILS OR THE LIKE Filed Feb. 20, 1943 4 Shets-Sheet 1 lllllllll I l N VEN TOR Midmel \Alq ttein' ATTORNEY 'IAug- 8, 5 I M. WATTER 2,383,634-

MAIN FRAME STRUCTURE FOR AIBFOILSI OR' THE LIKE INVENTOR ATTORNEY M. WATTER Aug. 28 1945.

' 2,383,634 MAIN FRAME STRUCTURE FOR AIRFOILS OR THE LIKE 4 Sheets Sheet 5 Filed Feb. 20, 1943 INVENTOR Michael Waiter ATTORNEY Aug. 28, M. NATTE R I MAIN FRAME STRUCTURE FOR AIRFOILS OR THE LIKE Filed Feb. 20, 1943 4 Sheets-Sheet 4 Mi hqep Wuder A TTORNE Y Patented Aug. 28, 1945 in hermit ST R'UCTUEE roam I 'ro'nas ORTHE LIKE- jct l' wa n iliii hia; n. set f j' Edward G. Budd Manufacturing Company,

emanation or Pefi'iisyT- Philadelphia, rat; a vania A 'anthemFetmryzo, 1943, seen to; 476,535 c'olrrms (o1; ice- 36M The? inventionrelates to the main IOa'd carrying frame of airfoils such as that provided the-main wings or fixed tail surfaces ofairplanes;-

HMoreiiartioula-rly it relates. to a joint between two load-carryingirame members,- such as aspar and aribywhich normally cross'each other at substantially right angles,- and to the construction of the. members and the joint between them which facilitatestheir fabrication and assembly and provides an assembled structure in, which the membersare not mater-ialiy weakened-where they cross each other, but are rather mutually interbraced to provide a strong frame structure capable of carrying all the loads to which it is ;..lI;t:is' a particular object of the inventionto provide a structure of this class wh-ioh'may be, readily. built up of light=gauge high "strength, suehias: stainless steel, shectlmetali members so formed as, the final assembly; to impart the? maximum of strength for theminimum'of weight, andso a's .to facilitate the ljoinde'r'of the parts Bysim'ple spot welding operations.

FI'hisatnda other objects are large part at-'- tained' by the construction and combination of parts which will be described;- in full the iol lowing detailed description forming a part hereof, ,Ihathe drawings in: which a preferred-*eiiribodi meht of the invention is: shown as applied to' an aircraft structure; r Fig.1 is a" plan view of a horizontal stabilizer through the portion of i the rib shown in: Fig. 6. approximately in .the location indicated by the line 1 Fig 3;

I Fig; is a detail perspective viewl ofan angle strip forming part of the: joint between the rib sections; ,1 a I v Fig; -9 is airagmentary perspective view of the portio'nof the spar shown in Figf 2,..with the rib removed therefrom: andaachanner securin andfillerstrip located laterally ofi the. sparin .posi-. tionfor movement laterallyxinto theslot in the spar; V 1

I Fig. 10 is a View similar to;Fig 6 but showing the rib sections inaseparatedt relation, as they appearprior to;final:a-ssembly.5.,- v c In the. drawings, referring to; Fig.2 .1, there is shown inzplarr-tatstabiliaer l' 0 itheframe ,of which comprises the main rear spar- .I I extending from tip' to tip; the; short intermediatelspar [-2 and thernoseostructur'e lt3'serving as aafrontspar and." extending also from tipto tip; The three spars V II, I12 and I73 are connectedcentrally by a strong rib- I 4* and adjacent: the ends of the intermediate spar by additional strong ribsaPi; i 51; "Additional ribs IG- interconnect the nose t3 and the inter-' mediatespar'and, outwardly ot-the ribs IS, the

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for-an. airplane; in which the invention is shown nose, Wand rea'r spar; are interconnected by additional suitably spaced ribs, designated). I31; certain of cthesenribs have hinge brackets as, t8- secured to them for supporting the elevator at; the trailing edge of the-tflbili2et The tips I-9 secured to outer ends of the spars I I ar-id-Hi' complete the ends; of the. stabilizer; Allparts ofthe framing of :the stabilizer are suitably. 'c oyered by a sheet metal skin-curved-to givethe desired aerodynamic characteristics to the stabilizer.

lien in the region indicated" by the dot anddash tion'thfough the stabilizer showing the rib eleva'tion in .thei'region where it passes through the Fight is 'aifragmentar-y elevational view,- on arredu'cedi scale-as compared with Fig) 3, of "the dentral pcrtiiirr of this spar; I y i l, t

-.Fig;.1=5; is affragmentary "horizontal sectional:

View ofcthe rib and spar at, -th'eir, intersection;

lower; rib chord passes through relations.

N The structure to whichthe present invention particularly relatescenters; about the section indicated by the :dot' and-dash circle indicated in Fig.1," Where-the-strongrib-l4 inter-sects the intermediate spar I2, althoughitgwil-l be understood that this: structure. ,mayj eflused in other As shown in chords zfl 'andzl interconnected byastiif Weflo 2-2.

As shown; the web consists cr mp-che tah reihatoroedby a transversely corrugated sheet 24 rigidly secured thereto as bMSDOt Welding at the bottoms of-- the corrugations contiguous to the eet. Each of ns the oppo te ma n of th c mmsie We which an les cansh re d-inse t. we to tilev opposite sides by welding on of themto the Fi s- 2; 3; '5, andllpth s Zit i- I mediate spar qomprisesspaoedtop;and bottom the has match has 2:; flanks As clearlyshown in Fig. l, the spar 12 decreases gradually in height from the center outwardly to give the appropriate taper to the stabilizer from the center toward the tips and this necessitatesthat the chords be likewise inclined. To'facili- Q tate bending of the chord members so as to form d an angle at the center, the vertically-deep arms" ofthe angles 25 are cut outfwitha V-notch as shown at 21 and the remaining arm'is bent to the desired angle before securing the chords to the web.

When bent to the desired angle, they are secured to the web and a reinforcing bridging angle, as 28, is nested with each of theangular chord members 25, overlappingv it on oppositesidesyof the V-notch, and is spotwelded toiboth .arms of the respectivemembers 25,.thuscarrying substantially-the full strength. of ..the chords across the cut out portions. 1.

Another advantage of ,the1cut outportions in the chords of .the spars is that it permits aideeper overall rib to be extended through the spar, since the bridging angles 28 are .not as deepasthe chord angles 25, and'thus. permitsthe spacing of the marginal contoured portions of therib ust the right distance to enablexproper securement of the stringer reinforcedskin. blanket thereto and directlythroughfithe tops of the spar chords to the spar as well, as shown in Fig. 3.

At this central-locationof the spar |2 the flat plate 23 is discontinuous and its place and the place of the corrugated reinforcement is taken in this region by oneormore flanged channels, as 29, secured through-their outwardly'extending flanges to the double thickness margin of the web formed; by the fiat'plate andthe end contiguous corrugation. An additional channel 29 having but-one sidewall flanged,-and that inwardly, issecured through-its other unfla'nged side wall to theadjacent side wall of one of the channe1s29. r r I 1 A space or slot, as iclearly appears in Figs-4 and 9,is provided between opposing channels 29 and 29' to permitof thepassage o'f the central rib l4 therethrough-.- 1r 1 a 1 This strong central rib i4 is; for convenience of assemblywith the spar l2, made intwo sections, at forward-section 3fl and an aftsection 3l,seeFig.l0. V

Each section is formed with spaced marginal cap strips, as 32, interconnected by'a web plate, as 33, having a-wide overlap with the capstrips and spot welded thereto inthe overlap. -To stiffen the web against buckling, its side opposite the side overlapping the cap'strips is reinforcedb'y spaced vertical reinforcements 34 of flanged channel section spot weldedthereto' throughthe flanges of the channels. "The rib sections are further strengthened and stiffened by chord members 35 of generally rectilinear for-m and of generally hat-shaped cross section, these chord membersbeing secured along the line of overlap between the cap strips and web plate to: the

hollow portion of the hat-shaped section is-rela-' tively deep to afford great stiffness and of generally acute angular shape, this shape facilitating the formation of the joint between the rib sections as will be described hereinafter.

The chord members 35 of the two sections are arranged at a slight angle to each other, to allow making them rectilinear, while conforming to the fore' and aft taper of the airfoil, as clearly appears in 'Figs."2, 3 and 6, and those'of'the forward section, see Fig. 10, terminate some distance inwardly of the vertical margin of the web plate 33 and adjacent cap strip 32 of that section.- These chord members project laterally from theweb 33 a distance which prevents passing the deep hat-shaped section through the slot in the spar.

To permit this passage and at the same time prevent any appreciable weakening of the chords at theirv passage through the spar slot, the ends of the chords on the two sections have part of their height cut away, as indicated at 36, and in the final assembly these ends come to nearly abutting relation for convenience of access in spot welding the .parts together in final assembly, as shown in Fig-3, substantially in the plan of the aft faceof the webof the spar. X

- To reinforce the almost abutting :ends. of; the

chords andto compensate for the strength re movedrby cutting away theendsofv the:hatshaped section thereof, a bridging membezgias 31, as shown to be of flangedchannel sectionis positioned and secured as by spot welding to the web 33 and cap strip 32 of the forward rib sec-. tion, so asto overlap the flanges of the adjacent end of the chord member '35, which is oifsetto pass over the bottom of the channel of thei bridge ing member and secured by welding its flanges to the triple thickness of metal provided by the overlapping bottom of the channel 31,..the'cap strip 32 and the web plate 33, as clearly appears in Figs. 7 and 10; Additionally, an angularbar; as 38 is telescoped between the remaining por-. tions of the sides of the laterally projecting-hats.

section of the chord 35 at the cut away end thereof.

and spot welded to these portionsnof the sides thereof to strengthen the chords in this cut away region. This spot welding takes place before the end portion of the chord is spot welded to the triple thickness web above identified;:becau'se.before welding the ends of the hat-shaped section to the bar 38, it is first necessaryto bringthe remainingv portions of the angularsectionsides together into contact with theopposite sidesof-i the bar. This has the effect of narrowingthe distance-between the margins of the flanges on the chord 35, which could not take placetifxthese flanges had been previously weldedto the bridg-. ing member 31. .After the bar is;-so-welded to the chord 35 the flanges of the narrowediend portion (see Figs. 3 and 10) are:welde'd to-Jthe triple thickness of metal, above identified. p

a The aft. section of the rib has its chord 'mem-i bers 35 extended some distance forwardly of the web thereof, as shown in Fig. 10, to form a final: assembly joint with the bar 38 and the bridging member 31 to which it is successively j oined when the aft portion-is brought into finally assembled relation, as shown in Fig, 6, .in identically the manner in which the chord of the forward section is joined to these members.-Becausethe overlapping parts in this final assembly areall aft'of the spar, access is readily had for'makint cut away portions to restore the strength of the chords in this region, the webs of the sections overlapping; and secured together in the overlap.

may be part of the forward rib section sub assembly, and joined in final assembly to the aft rib section, but thisis not essential since access can be had for welding it to both sections in the final assembly.

As so joined the rib carries substantially its entire strength through the spar, yet is readily assembled therewith, by o'pen and accessible joints, facilitating the welding.

Finally, the rib I4, is securely fastened to the spar l2 and the slot in the spar is closed so that the parts mutually reinforce and brace each other by bringing a channel section securing and filler piece 4! into the slot between the opposed channels 29, 29' flanking the slotin the spar. This channel 4| is of a width equal to the width of the slot less the thickness of the web plate 33 of the rib. Obviously there is no vertical stiffener 34 on the web plate 33 in this region, a appears in Fig. 6.

When the securing and filler piece 4 l is brought in place between one of the channels 29, 29 and the web plate 33 it can be readily secured in place by welding one of its side walls to said one of the channels flanking the slot and its other side wall to the double metal thickness provided by the web and the other channel flanking the slot. The open channels readily permit accessibility for spot welding the parts together in this fashion.

The framework formed by the spars and ribs may be covered top and bottom by a skin blanket of any suitable form. In the drawings Fig. 2, there is shown a thin metal skin, as42, reinforced by spaced longitudinal stringers, as 43. This blanket is secured directly to the flanges of the spar through the double thickness metal provided by the stringer metal and skin and indirectly to the rib cap strips 32 by clips 44 secured to the stringers and cap strips. However, this particular method of skin blanket securement is merely illustrative herein, and is fully described and claimed in another copending application.

In Fig, 4, fixtures 45 have been shown for securing a vertical fin to the top of the stabilizer. These fixtures are merely illustrative and form no part of the present invention, being fully described and claimed in a separate application.

While the invention has been shown and described in a specific embodiment and applied in a given location in an airfoil, it will be understood that in its broader aspects it is subject to Wide modification and adaptation to use in other relations than those specifically shown and deand the chords of thesections being joined at the spar, the chords of the sections being partially cut away at the region of passage through the spar, and reinforcing means bridging the 2. A framework for an airfoil comprising a spar and a rib extending substantially at right angles to each other, the rib passing continuously through a slot in the spar, the rib being constructed in sections, one located principally on one side of the spar and the other on the other side, each section of the rib comprising a Web and chords, the chords of the sections where they passthrough the spar being partially cut away, and reinforcing means bridging the chords of the rib sections in the cut away region to render them in efiect continuous from one sec tion to the other, the webs of the sections also being secured to each other to render'the web of the rib continuous.

3. A rib for an airfoil comprising spaced chords and a sheet Web interconnecting the chords, the

rib being constructed in longitudinal sections for convenience of assembly with a spar, the chords being arranged on the sides of the webs so that their adjacent endsmeet each other substantially at the point of intersection of the rib with.a spar, means connecting the adjacent ends of the chords of the sections together upon the side of one of the Web sections, and means connecting the web sections together upon the side of one of the chord sections'to render the rib of substantially full strength throughout.

4. A load carryfing rib for airfoils divided into sections adapted for assembly with a spar from the opposite sides thereof, the rib extending continuously through a spar without appreciable diminution of strength in the final assembly, each rib section comprising a sheet Web and spaced chords secured to the Web and projecting 40 laterally thereof, the chords of the sections meeting each other at a slight angle, and means insecured to theends of the chords of said one section in subassembly and'arranged inwardly of the end of the web of said section, the ends of the chords of the other section extending beyond the web of said section and adapted in final assembly to overlap the web and bridging means of the other section and be secured thereto, the adjacent ends of the webs of the sections also overlapping and being secured together in final assembly.

6. A load carrying member comprising spaced chords and a web interconnecting the chords,

said chords being substantially of hat-shaped cross section and secured to the web through the base flanges of the section, and said chords, at, at least one end. thereof, having the top portion of the crown of the hat-shaped section cut away, and bridging means joining together the remaining sidesof the crown at said cut away portion, whereby the strength of the section in the cut away region is largely restored.

- MICHAEL WATTER. 

